The present invention relates to a method of checking the working and/or the operational state of breathing equipment prior to its use, and also to breathing equipment which includes an arrangement for checking at least one working or state parameter of the equipment.
It is absolutely necessary to ensure that the breathing equipment used by a diver or a fireman, for instance, is fully serviceable and faultless prior to entering non-breathable atmospheres, for instance when diving or when working in smoke-filled or toxic environment for instance.
Among other things, it is necessary to check that the system gas-supply is completely full and therewith contains the amount of breathing gas that can be expected to be consumed, that the hoses leading to the breathing mask are tightly sealed, i.e. will not leak to the surroundings and therewith reduce the amount of gas available for breathing, that gas is able to flow from the gas reservoir freely and without hinder and will arrive at the breathing mask in sufficient volumes, i.e. that there is practically no resistance to the air flow and that the pressure prevailing in the breathing mask is higher than ambient pressure.
The gas reservoir carried by the person concerned will normally have the form of a gas cylinder which contains breathing gas at a pressure of normally 300 bars, when the cylinder is full. The breathing gas is normally air, although under special circumstances may often contain at least 20 percent by volume oxygen and an inert gas, most often nitrogen and perhaps also helium. In some cases, for instance for diving to great depths, the breathing gas contains less than 20 percent oxygen by volume. Since the gas reservoir has a relatively small volume, it is important that the reservoir pressure is sufficiently high to supply the user with an anticipated maximum gas volume.
It is also important that the hoses or lines leading from the gas reservoir are tight and that the flow resistance presented thereby is sufficiently small for the gas reservoir to deliver to the user a quantity of gas which is large enough to satisfy the user""s requirements, even in the case of an extreme need. is extreme.
Another important safety problem concerns the gas pressure in the mask when the mask is in place. The mask pressure must be greater than the ambient pressure, so that non-breathable atmosphere. particularly toxic atmosphere, is unable to penetrate into the mask.
One object of the present invention is to provide a method whereby these functions and/or states can be checked prior to using breathing equipment.
Another object of the invention is to provide an arrangement by means of which at least one functional parameter or state parameter of breathing equipment can be checked prior to use.
The first of these methods is achieved in accordance with the invention with a method which is characterized by activating a control circuit which measures at least one functional parameter or state parameter, comparing the measured parameter value with a control value and indicating acceptable or insufficient values respectively when the set criterion is fulfilled or when it is not fulfilled.
The second object is achieved with an arrangement which includes breathing equipment, a programmed microprocessor, a sensor which is included in the breathing equipment and connected to the microprocessor, and an indicating arrangement connected to the microprocessor.
Advantageous embodiments of the present invention are set forth in the dependent Claims.
According to the present invention, the control circuit is activated either by sensing intermittently a functional parameter or a state parameter of the breathing equipment, comparing the sensed parameter value with the latest measured parameter value, and activating the control circuit when there is a significant difference between these values. Another method to activate the control circuit is to intermittently sense a functional parameter or a state parameter of the breathing equipment, to compare the sensed parameter value with a predetermined value, e. g. 10 percent, of the maximum value of said parameter and to activate the control circuit when the sensed parameter is equal to or greater then the predetermined value. Alternatively, the control circuit is activated manually, by pressing a start button for instance.